Modem semiconductor device packaging typically involves provision of a microelectronic lid over a semiconductor die (also referred to as a chip) to protect the die during transport. The microelectronic lid can be thermally conducted with the die so that heat generated from the die is dispersed into the lid. Accordingly, the lid can function as a heat spreader in addition to functioning as a protective cover for the die.
A prior art semiconductor package is described with reference to FIGS. 1-4. Referring initially to FIG. 1, the package comprises a base 10 and a lid 30, which are initially provided as separate pieces. Base 10 can comprise a substrate 12, which can be a circuit-retaining construction, such as, for example, a circuit board. A semiconductor chip 14 is provided in electrical connection with the circuit of circuit-retaining construction 12, and can, for example, be connected to such circuit through solder bead electrical interconnects (not visible in the view of FIG. 1). A sealant material 16 is provided around an outer periphery of circuit-retaining construction 12, and can comprise, for example, an epoxy. The surface of base 10 that is shown in FIG. 1 will ultimately be an inner surface in a package construction formed with lid 30.
Referring next to lid 30, such comprises a recessed surface 32 surrounded by a non-recessed peripheral portion 34. Lid 30 also comprises a surface 36 that is in opposing relationship to surface 32, and accordingly that is a hidden underside of lid 30 in the view of FIG. 1. The surface 32 of lid 30 will ultimately be an inner surface of the lid in a package formed with lid 30 and base 10, and the surface 36 will be an outer surface of such package.
FIG. 2 shows a top view of a package 40 comprising lid 30 and base 10. A process step in formation of package 40 is to invert lid 30 from the configuration shown in FIG. 1, and to press the lid over base 10. Lid 30 is sealed to base 10 by sealing peripheral portion 34 of lid 30 to the base with sealant material 16.
FIG. 3 shows a cross-sectional view through the package 40 of FIG. 2, and illustrates lid 30 joined with base 10. Also visible in FIG. 3 are electrical interconnects 42 extending downwardly from chip 14 to electrically connect the chip with circuitry (not shown) retained in substrate 12. Additionally, FIG. 3 shows a thermally conductive interface material 44 provided on chip 14 and thermally connecting lid 30 with chip 14 to allow heat dispersion from chip 14 into lid 30. If material 44 were not present, or were replaced with a non-thermally conductive material, lid 30 would simply be a microelectronic lid. However, if material 44 is a thermally conductive material, lid 30 functions as a heat spreader, with the term heat spreader understood to indicate a construction that primarily spreads heat in two dimensions, rather than in three dimensions.
FIG. 4 illustrates the package 40 of FIG. 3 attached to a heat sink 50 through a thermally conductive interface material 52. Material 52 can comprise, for example, GELVET™, which is commercially available from Honeywell International, Inc. Heat sink 50 can comprise, for example, aluminum having a shape which incorporates numerous projecting fins and/or posts. The heat sink 50 is distinguished from a heat spreader, in that heat sink 50 disperses heat in three dimensions, rather than two.
It can be problematic and costly to fabricate a lid having the complexity of lid 30. Accordingly, it would be desired to develop improved microelectronic lid designs.